Compact dielectric resonator antenna

ABSTRACT

A dielectric radiator antenna arrangement for a communication device having a ground plane is provided. The antenna arrangement may include a dielectric volume having a central axis normal to the ground plane, and mode-exciting elements. The mode-exciting elements may include a first mode-exciting element provided in or attached to the dielectric volume and extending in a plane provided at a first distance from the central axis perpendicular to the ground plane, and a second mode-exciting element provided in or attached to the dielectric volume and extending in a plane provided at a second distance from the central axis and perpendicular to both the ground plane and the plane of the first mode-exciting element. The antenna arrangement can be used for simultaneously transmitting and receiving more than one signal at one frequency with reduced coupling.

RELATED APPLICATIONS

This application claims priority under 35 U.S.C. § 119 based on U.S.Provisional Application Ser. No. 60/805,536, filed Jun. 22, 2006, thedisclosure of which is incorporated herein by reference.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to the field of antennas and moreparticularly, to a dielectric resonator antenna arrangement, as well asa portable communication device including such an antenna arrangement.

DESCRIPTION OF RELATED ART

MIMO (multiple input, multiple output) is an antenna technology forwireless communications in which multiple antennas are used at both thesource (transmitter) and the destination (receiver). The antennas ateach end of the communications circuit are combined to minimize errorsand optimize data speed. MIMO-based antennas are of interest in relationto communication such as digital TV, WLAN, and in mobile communications.MIMO arrangements are of particular interest for use in wirelesscommunication, such as in portable communication devices, for instancecellular phones.

However, the size of a cellular phone is preferably small, and it istherefore disadvantageous to include more than one antenna in such adevice. This becomes even more of a factor as cellular phones need tocommunicate in different types of systems. This means that if the MIMOconcept is used for a small portable communication device, it may bedifficult to provide antennas in the device that have a low incidence ofcoupling to each other, especially if the device is to be kept small.

In recent years, a new type of antenna has evolved that is small and hasa high radiation efficiency, and is therefore of interest for use incellular phones. In a dielectric resonator antenna, a probe can excite atransmission mode in a resonating dielectric antenna volume.

US 2004/0155817 describes a multi-polarization dielectric resonatorantenna having three mutually orthogonal feeds, where the feeds extendradially from a central axis of the volume. These feeds havepolarizations at 120 degrees to each other and therefore allow thetransmission and/or reception of signals in three polarizations,simultaneously.

However, when applying a dielectric resonator antenna type in a MIMOsystem and using it for the transmission of two or more signals usingthe same frequency, a high coupling often occurs between the differentantenna signals. The occurrence of the coupling may seriously degradethe performance of such an antenna.

It would therefore be beneficial to provide a dielectric resonatorantenna that can be used for simultaneously transmitting and receivingmore than one signal at the same frequency and where the incidence ofcoupling between these antenna signals is reduced.

SUMMARY OF THE INVENTION

The present invention is generally directed to providing a dielectricresonator antenna arrangement that can be used for simultaneouslytransmitting and receiving more than one signal at the same frequencyand where the incidence of coupling between the antenna signals isreduced.

Implementations consistent with the principles of the present inventionprovide a dielectric resonator antenna arrangement that can be used forsimultaneously transmitting and receiving more than one signal at thesame frequency and where the incidence of coupling between these antennasignals is reduced.

According to one aspect, a dielectric resonator antenna arrangement maybe provided on a ground plane and may include a dielectric volume havingan axis substantially in the center of the volume provided as a normalto the ground plane, and a number of mode-exciting elements including, afirst mode-exciting element provided in or attached to the dielectricvolume and extending in a plane provided at a first distance from thecentral axis and being perpendicular to the ground plane, and a secondmode-exciting element provided in or attached to the dielectric volumeand extending in a plane provided at a second distance from the centralaxis and being perpendicular to both the ground plane and the plane ofthe first mode-exciting element.

Additionally, an antenna arrangement may include the features of thefirst aspect, wherein the first and second distances are equal.

Additionally, an antenna arrangement may include the features of thefirst aspect, wherein the first and second mode-exciting elements areprovided adjacent the ground plane.

Additionally, an antenna arrangement may include the features of thefirst aspect, further including a third mode-exciting element in thecenter of the dielectric volume normal to the ground plane.

Additionally, the third mode-exciting element may extend from a bottomsurface of the dielectric volume that is parallel to and faces theground plane.

Additionally, an antenna arrangement may include the features of thefirst aspect, wherein at least one mode-exciting element is acapacitively fed slot.

Additionally, an antenna arrangement may include the features of thefirst aspect, wherein the volume includes more than one dielectricmaterial with different dielectric constants, where the materials areprovided in a direction from the central axis and outwards and eachouter material completely surrounds an inner material.

Additionally, an antenna arrangement may include the features of thefirst aspect, wherein the dielectric volume is cubical.

In other implementations consistent with the principles of the presentinvention is to provide a communication device that includes adielectric resonator antenna arrangement, which can be used forsimultaneously transmitting and receiving more than one signal at thesame frequency and where the incidence of coupling between these antennasignals is reduced.

According to a another aspect, a communication device may comprise aground plane, a dielectric resonator antenna arrangement including adielectric volume having a central axis normal to the ground plane, anda number of mode-exciting elements including, a first mode-excitingelement provided in or attached to the dielectric volume and extendingin a plane provided at a first distance from the central axis and beingperpendicular to the ground plane, a second mode-exciting elementprovided in or attached to the dielectric volume and extending in aplane provided at a second distance from the central axis and beingperpendicular to both the ground plane and the plane of the firstmode-exciting element, and a separate signal feeder for eachmode-exciting element.

Additionally, a communication device may include a portablecommunication device.

Additionally, a communication device may include a cellular phone.

Implementations may provide radiation patterns associated with differentmodes that are orthogonal to each other. Also the polarizations may beorthogonal. Because of this, there may result a low correlation orcoupling between the modes together with a high efficiency, whichenables them to be used simultaneously for the same frequency, forinstance in MIMO applications. The antenna arrangement may be providedas a single component, which may be a surface mount component. Thecomponent may be very small and does thus not occupy much space within acommunication device. Such a component may be easily mass-produced andtherefore allow the provision of an inexpensive antenna arrangement. Thecomponent may be readily mounted on a circuit board

It should be emphasized that the term “comprises/comprising,” when usedin this specification, is taken to specify the presence of statedfeatures, integers, steps, or components, but does not preclude thepresence or addition of one or more other features, integers, steps,components, or groups thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described in more detail in relationto the enclosed drawings, in which:

FIG. 1 shows a front view of a portable communication device in the formof a cellular phone

FIG. 2 schematically shows a side view of a dielectric resonator antennaarrangement, according to one implementation, provided above a circuitboard including a ground plane

FIG. 3 shows a perspective view of the dielectric resonator antennaarrangement, according to one implementation, provided above the groundplane

FIG. 4 shows a view from above of the dielectric resonator antennaarrangement according to the present invention provided above the groundplane

FIG. 5 schematically shows capacitive feeding of a mode-exciting elementin the dielectric resonator antenna arrangement, according to oneimplementation; and

FIG. 6 schematically shows a dielectric volume comprising materialshaving different dielectric constants.

DETAILED DESCRIPTION OF EMBODIMENTS

FIG. 1 shows a front view of a (portable) communication device 10, forexample, in the form a cellular phone. The various functional units ofcommunication device 10 may be provided inside a housing that may beprovided with openings through which a display 14 and a keypad 12 may beprovided. Communication device 10 may include at least one antennaarrangement, which, according to an implementation consistent with theprinciples of the invention, may be provided in the housing ofcommunication device 10. A phone is just one type of portablecommunication device. Other examples are PDAs (Personal DigitalAssistants) and laptop computers. The invention is furthermore notlimited to portable communication devices, but may be used in stationarycommunication devices, for instance, in base stations.

FIG. 2 shows a side view of an antenna arrangement 18, according to oneimplementation, provided on a (circuit) board 16 including a groundplane 17. On board 16, a radio circuit (not shown) may be arranged tofeed antenna arrangement 18 with a number of (radio frequency) signals,for example, three signals. The signals may have the same frequency.Antenna arrangement 18 may be configured to also receive three signalsthat may have the same frequency and forward these to the radio circuitfor further processing. As such, antenna arrangement 18 may be providedfor a MIMO-type system.

Antenna arrangement 18 may be a dielectric resonator antenna andtherefore, may take the shape of a defined volume, at least partiallyfilled with a dielectric material 20. The volume may thus becharacterized as a dielectric volume, shown here as a cube. The shape ofthe volume may be dimensioned for resonating at the above-mentionedfrequency and with at least two different modes, for example, a TEM modeand in a HEM mode. Other modes are possible. Antenna arrangement 18 mayinclude mode-exciting elements 22, 24, 26 that may be arranged toexcite, for example, three modes within the cube.

One implementation is shown in more detail in a perspective view in FIG.3, and also in a plan view in FIG. 4. In relation to the cube, there isshown a three-dimensional coordinate system, with x-, y- and z-axes,where the z-axis goes upwards from the middle of the cube at a bottomside of this cube that faces ground plane 17. The z-axis is thus anormal of ground plane 17 and in this way, may define a central axis ofthe cube. The x-axis starts from the same point in the middle of thecube and continues in the middle between a right and a left bottom sideof the cube and in parallel with these sides in a direction towards afar short side of ground plane 17 and thereby crosses a far bottom sideof the cube at right angles. The y-axis starts from the same point inthe middle of the cube in the middle and continues between a frontbottom side and a back bottom side of the cube and in parallel withthese sides in a direction towards a right long side of ground plane 27and thereby crosses the right bottom side of the cube at right angles.First mode-exciting element 22, may be in the form of a rectangularprobe and provided in a plane parallel to the xz-plane at a distance d1from the central axis z and on a right vertical side of the cube at abottom side thereof. The plane that first mode-exciting element 22 isprovided in may also be perpendicular to ground plane 17. Secondmode-exciting element 24, may be in the form of a rectangular probe, andprovided in a plane parallel to the xy-plane at a distance d2 from thecentral axis and on a far vertical side of the cube at a bottom sidethereof. The plane that second mode-exciting element 24 is provided inmay be perpendicular to ground plane 17 and also to the plane in whichfirst mode-exciting element 22 may be provided. First and secondmode-exciting elements 22, 24 may be provided adjacent ground plane 17.Third mode-exciting element 26 may be in the form of a pin, and mayextend from the bottom side of the cube that faces ground plane 17 andalong the z-axis, i.e. along the central axis. Each mode-excitingelement 22, 24, 26 may be connected to a separate signal feeder (notshown) of communication device 10 to receive a separate signal.

This exemplary placing of first mode-exciting element 22 may excite aHEM mode of the electrical field of the cube, which field may provide afirst radiation pattern rp1 that may be semi-spherical and providedsymmetrically around the y-axis in a plane parallel to or within thexy-plane and having a horizontal extension. Second mode-exciting element24 may also excite a HEM mode of the electrical field of the cube, whichfield may provide a second radiation pattern rp2 that may besemi-spherical and provided symmetrically around the x-axis in a planeparallel to or within the xy-plane and also having a horizontalextension. Third mode-exciting element 26 may provide a third radiationpattern rp3 that may be a vertical omni directional pattern provided inthe yz-plane.

With this exemplary placing of mode-exciting elements 22, 24, 26,radiation patterns rp1, rp2 and rp3 that are orthogonal to each othermay be provided. Also, the polarizations may be orthogonal. There mayfurthermore a low correlation or coupling between the modes togetherwith a high efficiency, which enables them to be used simultaneously forthe same frequency in MIMO applications.

A number of variations may be made to antenna arrangement 18. Forexample, first and second distances d1 and d2 may be equal.Alternatively, first and second distances d1 and d2 may differ from eachother, while remaining orthogonal to each other. First and seconddistances d1 and d2 may be provided at the same distance above groundplane 17, or may be provided at different distances to ground plane 17.First and second mode-exciting elements 22, 24 may also be providedfurther away from ground plane 17. As shown, each mode-exciting elementis also directly fed by a radio signal from the radio circuit.Alternatively, it is also possible that either first mode-excitingelement 22 or second mode-exciting element 24 or both first and secondmode-exciting elements 22, 24 may be provided as slots 28 and 30 incircuit board 16. Such a slot may then be capacitively fed for excitinga HEM mode in the cube. This is schematically shown in FIG. 5, which inall other respects include the same elements as FIG. 3.

It is furthermore possible to provide the volume with more than onedielectric material, where the dielectric constant of the materials maydiffer. Therefore, a first dielectric material 20 may be substantiallysurrounded by a second material 32, where the materials areconcentrically provided outwards from the central axis. This isgenerally shown in a perspective view in FIG. 6. In this implementation,possible to provide different materials may be used for the dielectricvolume.

In the described implementation, the volume was provided in the form ofa cube. It should be realized that the invention is in no way limited toa cube or any other particular shape. The volume may be spherical,hemispherical, cylindrical, half-cylindrical, circular, half-circular,have pyramid shape or combinations of these shapes. The volume may beany type of regular or irregular shape. The mode-exciting elements havebeen described as provided on the outer side of the dielectric material;however, the mode-exciting elements may be provided inside the materialas well, at a distance from the central axis and, for example,orthogonal to one another. The mode-exciting elements may then beprovided in cavities provided in the dielectric material, for example.Other configurations are possible.

The mode-exciting elements may be provided by printing or paintingmetal, for example, on the dielectric material or by inserting metalelements in drilled holes in the dielectric material. Accordingly, it isfurthermore possible to provide antenna arrangement as a singlecomponent, which may be a surface mount component. The component may bevery small and thus may occupy limited space within a portablecommunication device. Such a component may be easily mass-produced andthus permits the provision of an inexpensive antenna arrangement. Sinceit is a component, it may be readily mounted to a circuit board, forexample, or any other substrate.

1. A dielectric resonator antenna arrangement to be provided on a groundplane, comprising: a dielectric volume having a central axis normal tothe ground plane; and at least three mode-exciting elements, including,a first mode-exciting element provided in or attached to the dielectricvolume and extending in a plane provided at a first distance from thecentral axis and being perpendicular to the ground plane, a secondmode-exciting element provided in or attached to the dielectric volumeand extending in a plane provided at a second distance from the centralaxis and being perpendicular to both the ground plane and the plane ofthe first mode-exciting element, and a third mode-exciting elementcentrally disposed in the dielectric volume extending along the centralaxis in a direction normal to the ground plane, wherein each of themode-exciting elements connects to a separate signal feeder.
 2. Theantenna arrangement of claim 1, wherein the first and second distancesare equal.
 3. The antenna arrangement of claim 1, wherein the first andsecond mode-exciting elements are provided adjacent the ground plane. 4.The antenna arrangement of claim 1, wherein the third mode-excitingelement extends from a surface of the dielectric volume adjacent theground plane.
 5. The antenna arrangement of claim 1, wherein at leastone mode-exciting element is a capacitively fed slot.
 6. The antennaarrangement of claim 1, wherein the volume comprises a plurality ofdielectric materials having different dielectric constants, wherein thedielectric materials are provided concentrically about the central axisand an outer one of the dielectric materials completely surrounds aninner one of the dielectric materials.
 7. The antenna arrangementaccording to claim 1, wherein the dielectric volume is cubical.
 8. Acommunication device comprising: a ground plane; a dielectric resonatorantenna arrangement including: a dielectric volume having a central axisnormal to the ground plane, and a number of mode-exciting elements,including, a first mode-exciting element provided in or attached to thedielectric volume and extending in a plane provided at a first distancefrom the central axis and being perpendicular to the ground plane, asecond mode-exciting element provided in or attached to the dielectricvolume and extending in a plane provided at a second distance from thecentral axis and being perpendicular to both the ground plane and theplane of the first mode-exciting element, and a third mode-excitingelement centrally disposed in the dielectric volume extending along thecentral axis in a direction normal to the ground plane; and a separatesignal feeder for each mode-exciting element.
 9. The communicationdevice of claim 8, wherein the communication device comprises a portablecommunication device.
 10. The communication device of claim 9, whereinthe communication device comprises a cellular phone.
 11. Thecommunication device of claim 8, wherein the third mode-exciting elementis entirely within the dielectric volume.
 12. The communication deviceof claim 8, wherein the first and second distances differ.
 13. Thecommunication device of claim 8, wherein a height of the firstmode-exciting element differs from a height of the second mode-excitingelement.
 14. The antenna arrangement of claim 1, wherein the thirdmode-exciting element is entirely within the dielectric volume.
 15. Theantenna arrangement of claim 1, wherein the first and second distancesdiffer.
 16. The antenna arrangement of claim 1, wherein a height of thefirst mode-exciting element differs from a height of the secondmode-exciting element.